This application is based upon and claims priority of Japanese Patent Applications No. 2001-259684, filed in Aug. 29, 2001, and Japanese Patent Application No. 2001-361504, filed in Nov. 27, 2001, the contents being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a condensed eight-ring aromatic compound which is suitably used in an organic EL element, an organic EL element using the condensed eight-ring aromatic compound, and an organic EL display using the organic EL element.
2. Description of the Related Art
Organic EL elements have features such as self-lighting, high-speed response, and the like, and application thereof to flat panel displays is expected. When a full-color flat panel display is realized by using organic EL elements, organic EL elements which can emit lights of the three primary colors (blue (B), green (G) and red (R)), respectively, are required.
For example, an organic EL element using a DCM dye is disclosed as an organic EL element which can emit red (R) light in C. W. Tang, S. A. VanSlyke, and C. H. Chen, xe2x80x9cJournal of Applied Physicsxe2x80x9d, Vol. 65, 3610 (1989). Further, organic EL elements, which use a porphin compound or a porphine compound which can emit red light, have been proposed in Japanese Patent Application Laid-Open (JP-A) No. 9-13024 (Japanese Patent Application No. 7-160676), JP-A No. 9-296166 (Japanese Patent Application No. 8-111437), JP-A No. 11-251061 (Japanese Patent Application No. 10-50464), JP-A No. 11-251062 (Japanese Patent Application No. 10-50465), a Japanese National Re-Publication (International Publication No. WO98/00474, Japanese Patent Application No. 10-503982), and the like. Moreover, an organic EL element using a bisanthrene compound which can emit red light has been disclosed in JP-A No. 11-144868 (Japanese Patent Application No. 9-303047).
However, with these organic EL elements, there is the problem that the color of the emitted light and the light-emitting efficiency are insufficient in actual use, and further improvements in actual use are required.
The present invention focuses on addressing these concerns, overcoming the aforementioned drawbacks of the prior art, and achieving the following object. Namely, an object of the present invention is to provide a condensed eight-ring aromatic compound which has high color purity of red light and excellent light-emitting efficiency, light-emitting luminance and the like and which is suitable for an organic EL element, an organic EL element which uses the condensed eight-ring aromatic compound and has high color purity of red light and excellent light-emitting efficiency, light-emitting luminance and the like, and an organic EL display which is high-performance and utilizes the organic EL element.
As a result of intensive studies carried out by the present inventors in order to overcome the above drawbacks, the present inventors discovered the following. Namely, specific condensed eight-ring aromatic compounds have high color purity of red light and excellent light-emitting efficiency, light-emitting luminance and the like, and are particularly suited for organic EL elements which are used for emitting red light. An organic EL element and an organic EL display using this condensed eight-ring aromatic compound have high color purity of red light and excellent light-emitting efficiency, light-emitting luminance and the like, and are high-performance, and can emit light at a higher luminance than conventional structures. Further, the condensed eight-ring aromatic compound has excellent transportability of positive holes (carrier) or electrons. An organic EL element and an organic EL display which use the condensed eight-ring aromatic compound in at least one of a positive hole transporting layer and an electron transporting layer have high color purity of red light and excellent light-emitting efficiency, light-emitting luminance and the like, are high-performance, and can emit light at a higher luminance than conventional structures.
In the condensed eight-ring aromatic compound of the present invention, a number of regions where substituents can be introduced is any of 14, 16 and 18, and the condensed eight-ring aromatic compound has a point-symmetrical skeleton. (However, excluding such cases in which the regions where substituents can be introduced are all hydrogen atoms.)
An organic EL element of the present invention comprises an organic thin-film layer including a light-emitting layer in between a positive electrode and a negative electrode, and the organic thin-film layer contains a condensed eight-ring aromatic compound, wherein the condensed eight-ring aromatic compound comprises a structure which has a number of regions where substituents can be introduced in any of 14, 16 and 18, and has a point-symmetrical skeleton.
The organic EL display of the present invention uses the organic EL element of the present invention.